The invention comprises a lean premix burner for a gas turbine and a method of operating a lean premix burner.
In detail, the invention comprises a lean premix burner with at least one fuel supply ring featuring primary fuel nozzles.
Such a lean premix burner can be realized as either an LPP module or a swirlcup.
Lean premix burners are known as state-of-the-art technology in a wide variety of designs and versions.
Lean premix burners were developed, among other reasons, to avoid formation of nitrous oxides. For this purpose, the air-to-fuel ratio is set high so as to realize a very lean mixture in this process. This results in relatively low burning temperatures in the main burning zone.
A potential drawback may result from the fact that the relatively low combustion temperatures lead to less complete combustion than at higher temperatures, resulting in unburned hydrocarbon and carbon monoxide emissions.
A further disadvantage is that the very lean mixture results in a combustion process that cannot be adjusted to much greater leanness under normal conditions without destabilizing the process. Setting the mixture leaner would finally result in a flame going out. This means that so-called pilot burners must be installed to ensure safe and air-worthy operation. These pilot burners ensure a high local combustion temperature. This, in turn, results in a high level of flame stability. A disadvantage to pilot burner operation is the relatively high level of resulting NOX emissions.
State-of-the-art technology comprises use of these pilot burners in axially staged combustion chambers used in combination with lean premix burners. Such combustion chambers are relatively large, feature a complex geometry and have a large surface requiring cooling.